Energy storage aerodynamic braking device and method

ABSTRACT

In order to generate an efficient aerodynamic braking force, whatever the speed of a vehicle such as an airplane flying in the air, the method includes a step for the production of energy by the vehicle, a step of storage of the energy produced and a step of utilization of such energy to drive a propeller which generates a force opposing the forward motion of the vehicle. Energy is produced by using the displacement of the vehicle with respect to air using a propeller driving a generator, or using the displacement with respect to the ground, using wheels driving a generator, or using generators driven by motors of the vehicle. The energy can be stored in the pneumatic, electric or kinetic form and the generation and driving means are selected according to the technology used for the storage means.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to International ApplicationPCT/FR2008/050474 filed 19 Mar. 2008, which claims priority to FrenchApplication No. 07 53929 filed on 20 Mar. 2007, the disclosures of whichare incorporated herein by reference in their entireties.

BACKGROUND

1. Field

The aspects of the disclosed embodiments relate to the field of thecontrol of airplane flights. More particularly, the aspects of thedisclosed embodiments relate to devices intended to act on the dragforce of planes generally grouped under the name of “airbrakes”.

2. Brief Description of Related Developments

The drag of airplanes is normally considered as a defect which must befought since the drag is opposed to the forward motion of the airplaneand increases the consumption of fuel.

However, there are particular times during the flight of a plane, whenit is useful to increase the drag so as to decelerate more quickly thanunder the simple effect of the ordinary drag of the airplane or in orderto avoid an excessive acceleration during a descent.

Being able to increase the drag at some times of the flight becomes allthe more useful since maximum efforts are made by the design teams toreduce the cruise drag.

To increase the drag, an airplane 1 includes airbrakes 2, generallycomposed of rigid elements positioned so as not to generate drag duringthe cruise flight and including one or several so-called deployedpositions, so that the rigid elements have a surface which opposes theforward motion in air. Many shapes of airbrakes, positioned on the wingsof the airplane or on the fuselage, exist and are used on civil ormilitary airplanes.

Such airbrakes are all the more efficient when the speed of the aircraftis high. More precisely, the drag force, thus the resultingdeceleration, is directly a function of dynamic pressure, i.e. is, for agiven position of the airbrakes, proportional to a term in ρv² where ρis the density of the fluid (air at the flight altitude) and V thedisplacement speed of the airplane with respect to the fluid.

The problem entailed in this braking means is the loss of efficiencywhen speed is reduced. It is, for example, 6 times lower at 50 m/s,which is the typical speed of a modern airplane at the time of thelanding, than at 125 m/s, which is the typical speed at the end of thedescent and it becomes negligible very rapidly when the speed is furtherreduced, more particularly after the landing.

Other means exist to slow down an airplane 1, more particularly afterthe landing, such as the reversal of the thrust direction of the motors3 of the airplane or the braking of the wheels 4 in contact with therunway.

Although they are largely used on civil planes, such means have numerousdefects.

Thrust inverters 5 used on reactors are complex, heavy and expensive toproduce as well to exploit. In addition to the mass penalty theyrepresent for the airplane, they reduce the performances of the motor innormal operation mode, because of the inevitable imperfections of suchdevices which induce aerodynamic drags and load losses which entailexcessive consumptions.

Braking systems of the wheels 4 are of a limited efficiency, when therunway is contaminated by water, snow or ice and their utilizationcauses brakes and tires friction elements to wear and so these must bereplaced all the more frequently when brakes are used intensively.

Then, there is a real interest in using means making it possible toobtain an efficient braking force of the airplane at any speed and whichmakes it possible to simplify the existing devices and to limit the usethereof in operation.

SUMMARY

In order to generate, at the right time, a breaking aerodynamic forcewhich is not penalized by the slow speed of a vehicle with respect toair, the present application provides a method for generating anaerodynamic braking force on the vehicle moving in a displacementdirection with respect to the mass of the surrounding air.

Said method includes:

-   -   a step of generation of energy by said vehicle,    -   a step of storage of the energy generated by said vehicle, and    -   a step of utilization of said energy for generating an        aerodynamic force which is different from the drag force, and        applied to the vehicle and substantially opposed to the        direction of the displacement.

Energy is stored in a form which can be used by the means whichgenerates the aerodynamic braking force, for example, at least partiallyin the form of kinetic energy or in the form of pneumatic energy or inthe form of electric or electrochemical energy.

In one embodiment of the method, the step of generation of energy by thevehicle includes a step during which the generated energy is sampledfrom the kinetic energy of the vehicle and/or a step during which thegenerated energy is produced by vehicle-mounted means.

When the stored energy is sampled from the kinetic energy of thevehicle, the sampling is carried out using the displacement of thevehicle with respect to the air mass, more particularly at times duringwhich the speed with respect to air is high and/or using thedisplacement of the vehicle with respect to the ground.

Advantageously, the sampling of energy from the kinetic energy of thevehicle is used for producing a deceleration of the vehicle and foravoiding or limiting the use of other braking means.

Advantageously, the intensity and direction of the aerodynamic brakingforce generated during the step of utilization of energy are modulatedfor matching the desired deceleration, and the aerodynamic braking meansare used for generating a passive aerodynamic drag which makes itpossible to avoid or to limit the utilization of specific airbrakes.

To provide efficient aerodynamic braking under any condition moreparticularly at low speed, the aerodynamic braking device of the vehicleaccording to the invention includes first vehicle-mounted means forproducing energy able to be stored, second vehicle-mounted means able tostore the energy generated by said first means and third vehicle-mountedmeans for generating an aerodynamic force from the energy stored in saidsecond means.

In one embodiment, the first vehicle-mounted means for producing energyincludes at least one propeller able to be driven in rotation by therelative displacement of the vehicle with respect to the air mass.

Said at least one propeller is coupled to at least one generator able toproduce energy able to be stored.

In another embodiment, when the vehicle includes wheels driven, at leasttemporarily, in rotation by the displacement of the vehicle on theground, the first vehicle-mounted means for producing the energyincludes at least one generator, able to produce energy, able to bestored, able to be driven in rotation by the rotation of the wheels.

The at least one generator able to produce energy able to be stored isadvantageously a compressor compressing a gas or an electric generatoror a hydraulic pump.

The second vehicle-mounted means able to store energy are static energystorage means including at least one compressed gas tank and/or anelectric or electrochemical storage battery and/or are energy kineticstorage means including at least one fly wheel able to rotate about oneaxis.

When the energy storage means uses a fly wheel, said fly wheel is drivenin rotation about its axis by a pneumatic motor and/or by a hydraulicmotor or it is mechanically coupled to the propeller operated in a windenergy mode.

Advantageously, to facilitate the installation of the fly wheel when thestorage means use a fly wheel, said fly wheel is capable of driving inrotation energy-generating means which includes at least one pneumaticcompressor and/or an electric generator and/or a hydraulic pump.

Advantageously, the means for driving in rotation the at least one flywheel is able to generate energy when it is driven in rotation by saidat least one fly wheel.

To obtain an aerodynamic braking force with a correct yield and asufficient intensity, the third vehicle-mounted means generating anaerodynamic force advantageously includes at least one propeller able tobe coupled to rotation driving means preferably including at least onepneumatic motor and/or one electric motor and/or one hydraulic motorable to be supplied by the energy stored by the second vehicle-mountedmeans.

Advantageously, the at least one propeller used by the third means forgenerating the braking aerodynamic force is also used by the first meansto produce energy able to be stored and the at least one generator ableto produce energy when it is driven by the at least one propeller isalso able to drive the propeller in rotation when it is supplied withenergy.

At the same time or alternatively, the storage means is able to besupplied with energy by generators coupled to vehicle-mounted powergenerators.

In order to control the load of the storage means and the brakingaerodynamic force, the device includes regulation means acting on thepitch of the blades of the at least one propeller.

To minimize the impact of the device on the vehicle aerodynamics, thedevice includes means for storing energy-generating elements oraerodynamic braking forces generating means in contact with theaerodynamic flow when they are used, in order to reduce the aerodynamicdrag when they are not used.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description of one embodiment of the invention is madewhile referring to the Figures which show:

FIG. 1: as already mentioned, a general view of an airplane and thevarious parts used during the implementation of the invention;

FIG. 2: a principle diagram of the invention and its major components;

FIG. 3: a principle diagram of one embodiment of the invention usingcomponents with a reversible operation;

FIG. 4: a principle diagram of an embodiment of the inventionimplementing a kinetic storage of energy and a wind energy mode forenergy collection;

FIGS. 5 a and 5 b: a cross-sectional view of an exemplary installationof the device according to the invention in the wings of a plane, in anoperational position in FIG. 5 a and stored position in FIG. 5 b.

DETAILED DESCRIPTION

A method according to the invention consists of a first step to store anavailable energy aboard the plane, by sampling this energy using meansand during steps of the flight during which said sampling of energy fromthe performances of the plane is advantageous or acceptable, as regardsdegradation, and in a second step, to use the energy stored forgenerating an aerodynamic force opposed to the forward motion speed ofthe plane.

In a first implementation of the method, the stored energy is sampledfrom the kinetic energy of the plane 1 and is generated by using speed Vof the plane 1 with respect to air.

Energy is sampled using at least one propeller 10 integral with theplane 1 and operated in a so-called wind energy mode, i.e. the propelleris driven by the relative speed of the flow caused by the displacementof the plane 1 in air.

The rotation of the shaft 11 of the propeller 10 is connected to therotating shaft of a generator 12, so that the generator 12 is driven bythe rotation of the propeller 10. The generator 12 is selected so as toproduce energy capable of being transported by transfer means 16 to bestored in vehicle-mounted storage means 13. Control and regulation means17, for example controlled by a computer not shown, are associated withthe means for generating, transporting and storing energy.

A method consists in storing energy in the form of a compressed gas inat least one storage tank of the storage means 13, for example air, andin this case the generator 12 advantageously includes compression meanswhich are coupled to the propeller 10. When the propeller 10 is drivenin rotation by the relative displacement of air about the plane 1, thecompression means compresses gas, for example, air sampled from theplane environment, and this compressed gas is sent to the at least onestorage tank to be stored using ducts including means such as valves,non-return valves, probes and regulators useful in the operation of thedevice.

Another method consists in storing energy in the electric form inelectric or electrochemical cell batteries associated with storage means13 and in this case the generator 12 advantageously includes electricgeneration means coupled to the propeller 10. When the propeller 10 isdriven in rotation by the relative displacement of air about the plane,the electric generation means produces electric energy which is used forcharging the cell batteries.

Another method consists in storing energy in the kinetic form usingkinetic storage means including at least one fly wheel 14 driven inrotation by driving means capable of coupling the shaft 11 of thepropeller 10 and the shaft of the at least one fly wheel. In this case,the energy stored depends on the rotation speed ω of the fly wheel orwheels 14 and the driving means is advantageously capable of varying theratio between the rotation speed of the shaft 11 of the propeller 10 andthe rotation speed ω of the at least one fly wheel 14.

These driving means with a variable ratio may, for example, consist ofan assembly of pinions, various relative positions of which make itpossible to obtain different rotation speed ratios between an inputshaft and an output shaft. They can also consist of hydraulic drivingmeans, wherein the propeller 10 drives a hydraulic pump and the at leastone fly wheel 14 is driven by a hydraulic motor coupled to said pump,said pump and/said motor having variable displacements.

They may also consist of electric or pneumatic driving means, whereinthe propeller 10 drives an electric or pneumatic generator and the atleast one fly wheel 14 is driven by an electric or pneumatic motorcoupled to the generator associated with the driving means.

Regulation means, not shown, is advantageously implemented so that thedevice intended to generate energy and to store said energy is operatedwithin the various mechanical and/or electric and/or hydraulic and/oraerodynamic limitations met by such means. More particularly, thepropeller 10 advantageously includes variable pitch blades 15 and thepitch is modified, in a controlled way, by the regulation means as afunction of the rotation speed of the propeller and the load of thepropeller.

When energy is stored in vehicle-mounted storage means 13, said energyis used for generating an aerodynamic braking force using a propeller 20coupled to a motor 21 connected to the storage means 13 by energytransfer means 18, the rotation direction and the pitch of which areselected so as to cause on the plane 1 a force opposed to the directionof displacement of said plane in air. The force created by thispropeller 20 has the advantage of:

-   -   being capable of a modulation in intensity more particularly by        acting on the means 19 controlling the power delivered by the        motor 21;    -   keeping a high intensity when the speed V of the plane is low,        which is not possible with the conventional airbrakes 2.

The motor 21 which drives the propeller 20 during the aerodynamicbraking phases is adapted to the energy storage mode and restitutionmode. Preferably, the motor 21 is a pneumatic motor when energy isstored in accumulation means 13 in the form of compressed gas or anelectric motor when energy is stored in electric cell batteries.

When energy is stored in the kinetic form, the propeller 20 is driveneither by a mechanical connection with the fly wheel 14, the fly wheel14 being used as a motor rotor, or the fly wheel 14 drives a generatorwhich can be, for example, a hydraulic, a pneumatic or an electric one,and the propeller 20 is driven by a motor coupled to the generator anddriven by the fly wheel adapted to the selected technology.

Advantageously, some means used for implementing the step of storingenergy and for the step of creating a braking aerodynamic force are thesame and selected so as to be operated in a reversible way, asillustrated in FIGS. 3 and 4.

More particularly, the propeller 30 which is used for generating theaerodynamic braking force, when it is driven by a motor, isadvantageously used for producing energy to be stored, by driving agenerator. The (pneumatic, hydraulic or electronic) generator is thenpreferably selected first to be capable of being operated in motor mode,depending on whether the device is operated in energy-storage mode or inbraking aerodynamic force creation mode.

Such generators/motors 31, the operation of which is reversible, arewell-known in hydraulic, pneumatic and electric fields, and it ispossible to reduce the mass, the volume and the cost of the deviceaccording to the invention when using a motor/generator 31 coupled tothe propeller 30 and a motor/generator 32 coupled to kinetic storagemeans if such means is used.

So as not to generate an inacceptable drag penalty during the cruiseflight, when the device is not used, the propeller 10, 20, 30 isadvantageously folded, which means that the blades 15 of the propellerare positioned with their axes substantially parallel to the rotationaxis of the propeller.

In another embodiment, not shown, the propeller is carried by amechanical device which makes it possible to store the propeller, withthe blades folded or not, when said propeller is not used in a recessprovided for this purpose.

The components (generators, motors, storage means and control andregulation systems of the device) are preferably distributed in volumesavailable along the fuselage 7 and/or the wings 6 of the plane 1. Whenthe constraints of installation of the various components, moreparticularly the distance between the storage means and the generationmeans and/or the motors must be limited, for example for pneumatic orhydraulic connections, the components can be assembled in volumesprotected by aerodynamic fairings 8 which are advantageously associatedwith fairings of the plane which exist for other reasons, for examplefairings surrounding the slotted flap rails.

The energy to be stored which is produced by the propeller 10, 30coupled to a generator and driven in rotation by the effect of arelative displacement of the plane with respect to the air mass willpreferably be produced at a time, on the one hand when the aerodynamicbraking is desired since this production of energy generates a dragforce, and on the other hand when the speed of the plane is stillrelatively high in order to take advantage of a high dynamic pressure todrive the propeller and the generator coupled to said propeller. Theseconditions are met during the flight of the plane, for example duringthe descent from a cruise altitude to a stand-by or approach altitude,with speed V is high and the airbrakes 2 are frequently used to maintainor reduce the speed on the trajectory during the descent, or to descentmore quickly without the speed on the trajectory increasing. During thedescent phase, it is thus possible to take advantage of a high dynamicpressure to efficiently drive the propeller in wind energy mode or ingenerating an aerodynamic drag which causes the braking desired. Inaddition, the descent phase during which these conditions, i.e. highdynamic pressure and need for aerodynamic braking are met, generallycomes before a phase of flight leading to the landing, during which thedynamic pressure is much lower because of the reduced speed of the planeand during which it is useful, if not necessary, to use efficientaerodynamic braking means. When the aerodynamic braking caused by theoperation in wind energy mode of the propeller 10, 30 for storing energyis no longer sufficient, the energy stored in the means 13 is used fordriving a propeller 20, 30, preferably the same propeller 30 as alreadydescribed and dynamically generate an aerodynamic braking force.

In a second implementation of the method, the stored energy is sampledfrom the kinetic energy of the plane 1 and is generated using the speedof the airplane with respect to the ground, when the plane 1 has landed.

In this second mode, wheels 4 drive means 12 for generating energy ableto be stored by storing means 13 and/or to be used by aerodynamicbraking means.

Similarly to the first mode, the aerodynamic braking force is createdusing at least one propeller 20, the pitch and the rotation direction ofwhich generate on the airplane 1 a force opposed to the plane forwardmotion. Said at least one propeller 20 is driven by a motor 21 suppliedby the energy stored in the storage means 13.

For example, when the plane 1 lands and the wheels are rotated by thedisplacement of the plane on the runway, compressed air generation meanscoupled to the wheels is driven and produces pressurised air which isstored in at least one storage tank. Said pressurised air is used by apneumatic motor coupled to the at least one propeller for driving saidat least one propeller in rotation. The generation and storage means canuse another form of electric energy for example.

In this second mode, the storage means 13 is preferably means enabling aquick storage of energy. As a matter of fact, the running phase of alanding plane is short and the maximum energy must be sampled at thebeginning of the landing, when the running speed is maximum, thus thekinetic energy of the plane is still relatively high, to be used tocreate an aerodynamic braking force during the whole running phase. In aconjugated or alternative way, the energy produced by the generatingmeans coupled to the wheels 4 can be directly used by the aerodynamicbraking force generation means without being stored.

Besides, the sampling of energy from the wheels 4 to supply the brakingaerodynamic force generating means participates in the deceleration ofthe running plane, which makes it possible to limit the use ofconventional brakes.

In a third implementation of the method, the stored energy is producedby at least one motor 3 of the airplane 1. This motor can be used forthe propulsion of the plane or a motor of a power auxiliary unit.

In this third mode, the at least one motor 3 drives the means 12 forgenerating energy able to be stored and/or be used by aerodynamicbraking means. Advantageously, such generation means 12 is alreadyexisting and available means. As a matter of fact, most of the modernplane motors include electric generations and/or hydraulic generationsand/or generations of pressurised air able to generate energy which canbe stored, and it is not necessary to use additional generating means.

Advantageously, the energy stored is supplied by the at least one motor3 during phases of the flight of the airplane 1, during which theperformances of said motor are not critical, for example during thedescent which comes prior to the landing, if this is a motor used forpropulsion. In a conjugated or alternative way, the energy produced bythe at least one motor 3 can be directly used by the aerodynamic brakingforce generating means without being stored.

In all the embodiments of the invention, the at least one propeller 20,30 used by the device for creating an aerodynamic braking force isadvantageously used for creating a passive aerodynamic drag which can beadjusted, when the energy-storage means is not connected to thegenerator 12, for example when it has reached its maximum storagecapacity. The value of this aerodynamic drag can be modulated moreparticularly by acting on the propeller load in wind energy mode.

For all the embodiments, when the speed V becomes too low for theefficiency of other aerodynamic braking means using the generation of anaerodynamic drag to be satisfactory, because of the dependence thereofon dynamic pressure, the stored energy is used for driving in rotationthe propeller 20, 30, the pitch and the driving power of which areadjusted to supply a force opposed to the plane forward motioncorresponding to the aerodynamic braking desired.

According to the method, it is possible to obtain an aerodynamic brakingforce until the null speed of the plane on the runway, that is underconditions where the airbrakes are no longer useful, and thus to replaceat least partially the conventionally used devices to brake the plane 1when it has landed, as the thrust inverters 5 of the motors 3 and/or thewheel brakes 4.

Advantageously, a plane is equipped with two or more devices accordingto the invention or one device including two or more energy-generatingor aerodynamic braking propellers sharing the same energy-storage means.

To obtain a satisfactory efficiency of the aerodynamic braking andminimum impact on the performance during the cruise flight, the deviceis integrated in the plane on the aerodynamic plane.

The aerodynamic integration of the shapes of the plane belongs to theordinary work of aerodynamic designers.

Advantageously, the elements of the device will be integrated in volumesavailable in the structure, existing fairings 8 such as flap fairings orin fairings specifically designed for the device.

When the plane is provided with at least one aerodynamic brakingpropeller on either side of the plane of symmetry of the plane, forexample the wings, deviations of the aerodynamic braking forces betweenthe left and right sides make it possible to act on the side control ofthe plane, such as with conventional airbrakes but at much lower speedsor even null speeds.

Although the aerodynamic braking method and the associated means areapplied in the detailed description to a particular case of the plane,the persons skilled in the art will easily adapt the device to land orsurface vehicles which, under certain conditions, have benefit in usingaerodynamic braking means. Such conditions are more particularly metwhen the adherence of said vehicles to the ground does not make itpossible to generate sufficient braking forces by friction, for exampleon a slippery ground, to produce the desired decelerations.

The invention claimed is:
 1. An aerodynamic braking device for anaircraft including: a first aircraft mounted means that produces energy,a second aircraft mounted means that stores the energy generated by saidfirst means, and third aircraft mounted means that generates anaerodynamic force to brake the aircraft from the energy stored in saidsecond means, with said first means including at least one propellerable to be driven in rotation by the relative displacement of theaircraft with respect to the air surrounding the aircraft, said at leastone propeller being coupled to at least one compressor that compresses agas to be stored in the second means, the gas including air sampled fromair surrounding the aircraft; wherein the third means includes said atleast one propeller, said at least one propeller including blades thatare positioned with their axes substantially parallel to a rotation axisof said at least one propeller when said device is not in use.
 2. Adevice according to claim 1, wherein the aircraft includes wheelsdriven, at least temporarily, in rotation by the displacement of saidaircraft on the ground and the first aircraft mounted means includes atleast one generator that produces energy from the rotation of saidwheels.
 3. A device according to claim 1, wherein the energy-generatingmeans includes at least one pneumatic compressor.
 4. A device accordingto claim 1, wherein said at least one propeller is able to be coupled torotation-driving means.
 5. A device according to claim 4, wherein therotation-driving means includes at least one pneumatic motor and/or anelectric motor and/or a hydraulic motor able to be supplied by theenergy stored by the second aircraft mounted means.
 6. A deviceaccording to claim 4, wherein the at least one propeller of the firstmeans is mechanically coupled to energy kinetic storage means.
 7. Adevice according to claim 4 including regulation means acting on thepitch of the blades of the propeller or propellers.
 8. A deviceaccording to claim 1, wherein the at least one compressor able toproduce energy when it is driven by the at least one propeller is alsoable to drive the propeller in rotation when it is supplied with energy.